title: Consequences of anatomic changes and respiratory motion on radiation dose distributions in conformal radiotherapy for locally advanced non-small-cell lung cancer.
abstract: OBJECTIVE
  To determine the effect of interfractional changes in anatomy on the target and normal tissue dose distributions during course of radiotherapy in non-small-cell lung cancer patients.
  
  
  METHODS
  Weekly respiration-correlated four-dimensional computed tomography scans were acquired for 10 patients. Original beam arrangements from conventional and inverse treatment plans were transferred into each of the weekly four-dimensional computed tomography data sets, and the dose distributions were recalculated. Dosimetric changes to the target volumes and relevant normal structures relative to the baseline treatment plans were analyzed by dose-volume histograms.
  
  
  RESULTS
  The overall difference in the mean +/- standard deviation of the doses to 95% of the planning target volume and internal target volume between the initial and weekly treatment plans was -11.9% +/- 12.1% and -2.5% +/- 3.9%, respectively. The mean +/- standard deviation change in the internal target volume receiving 95% of the prescribed dose was -2.3% +/- 4.1%. The overall differences in the mean +/- standard deviation between the initial and weekly treatment plans was 3.1% +/- 6.8% for the total lung volume exceeding 20 Gy, 2.2% +/- 4.8% for mean total lung dose, and 34.3% +/- 43.0% for the spinal cord maximal dose.
  
  
  CONCLUSIONS
  Serial four-dimensional computed tomography scans provided useful anatomic information and dosimetric changes during radiotherapy. Although the observed dosimetric variations were small, on average, the interfractional changes in tumor volume, mobility, and patient setup was sometimes associated with dramatic dosimetric consequences. Therefore, for locally advanced lung cancer patients, efforts to include image-guided treatment and to perform repeated imaging during the treatment course are recommended.
authors.affiliation: Department of Radiation Physics, Division of Radiation Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX, USA.
authors.forename: Keith R
authors.initials: KR
authors.lastname: Britton
authors.forename: George
authors.initials: G
authors.lastname: Starkschall
authors.forename: Helen
authors.initials: H
authors.lastname: Liu
authors.forename: Joe Y
authors.initials: JY
authors.lastname: Chang
authors.forename: Stephen
authors.initials: S
authors.lastname: Bilton
authors.forename: Muthuveni
authors.initials: M
authors.lastname: Ezhil
authors.forename: Sandra
authors.initials: S
authors.lastname: John-Baptiste
authors.forename: Michael
authors.initials: M
authors.lastname: Kantor
authors.forename: James D
authors.initials: JD
authors.lastname: Cox
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Komaki
authors.forename: Radhe
authors.initials: R
authors.lastname: Mohan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001822:Body Burden; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009038:Motion; D011835:Radiation Protection / Q000379:methods; D011859:Radiography; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012062:Relative Biological Effectiveness; D015656:Respiratory Mechanics